1. Field of the Invention
The present invention relates to an actuator, in particular, an actuator for use in a focusing and tracking control apparatus in optical equipment, such as a compact disk player (CDP), laser disk player (LDP) or the like. The actuator operates to transfer, in a focusing direction or a tracking direction, an optical pickup of the optical equipment, which reads information stored on a disk.
2. Description of the Related Art
FIGS. 1A and 1B show winding structures of a focusing coil and a tracking coil in a conventional actuator. In particular, FIGS. 1A and 1B show winding structures of the coil wound around the optical pickup (not shown). As shown in FIG. 1A, focusing coil A', for transferring the optical pickup in a focusing direction, is wound about the sides of the optical pickup, and tracking coils B', for transferring the optical pickup in a tracking direction, are attached to the sides of focusing coil A'. Specifically, tracking coils B' are attached to either or both sides of focusing coils A', in such a manner that planes formed by the winding structure of each tracking coil B' are perpendicular to a direction of a magnetic field.
In FIG. 1B, a plane formed by focusing coils A' is parallel to a direction of the magnetic field, and planes formed by tracking coils B' extend along the axial direction of the magnetic field. Focusing coils A' are wound in the same manner as shown in FIG. 1A, while two kinds of tracking coils B' are wound in such a manner that they cross each other in a plane perpendicular to the direction of the magnetic field.
Various coil winding structures, such as those shown in FIGS. 1A and 1B, are known, and processes for fixing the coils to the optical pickup are often complicated. Further, a member which supports the optical pickup usually contains a spring device or the like, which imposes a large force on the actuator to facilitate movement of the actuator.
U.S. Pat. No. 5,177,640 to Grassens entitled "Two-Axis Moving Coil Actuator" discloses an actuator having tracking and focusing coils in a lens holder. The lens holder is disposed so as to be in a magnetic field generated by two pairs of permanent magnets. The tracking coil encloses the lens holder, and two focusing coils are fixed to the tracking coils adjacent to the permanent magnet pairs.